Pulmonary gas exchange immediately after birth in spontaneously breathing infants.

The pulmonary gas exchange (rate of oxygen consumption, VO2 and rate of carbon dioxide production, VCO2), heart rate, and transcutaneously measured oxygen saturation were measured during the first five minutes after birth in healthy newborn infants. Fifteen full term infants who were vaginally delivered, 15 full term infants born by caesarean section, and 10 preterm infants born by caesarean section were studied. VO2 tended to be slightly higher than VCO2 during the first minutes, with a gradual change to a respiratory exchange ratio above 1.0. VO2 and VCO2 were significantly higher in vaginally delivered infants than in those born by caesarean section during the second minute after birth, partly due to a higher number of cries/minute. During periods of calm breathing, VO2 and VCO2 were significantly higher in vaginally delivered infants than in those born by caesarean section, with low gas exchange levels in infants born by caesarean section during the second minute after birth. Decreased ventilation was reflected by a significant drop in oxygen saturation within 30-45 seconds.